A word of advice. Never use the phrase "just a burger" with Nancy Silverton. I did and was promptly challenged on every aspect of burger-making, starting with where to buy the meat, what grind, size of patty, how to cook it, what to serve with it, what pickle, what bun, what ketchup, what mayonnaise, what mustard, what cheese, how thick to slice the avocado, what bacon, what smoke on the bacon, what occasion.

The co-founder of Campanile restaurant and La Brea Bakery may be famous for more sophisticated food, but to her, the burger is one of the great American dishes, and exactly the thing that she likes to give friends for an end-of-summer barbecue. To prove it, she immediately threw a party.

I was the guest taking notes.

When we arrived midday, the fire was going in her barbecue pit. It was made from almond wood, lighted at 8 that morning to give it time to form its own charcoal. The hamburger toppings were already prepared, the buns sliced. The world famous chef was in her element. "I've always loved hamburgers," she cried, "back to the day I ate them at Denny's well done."

Over the years, the way that she made burgers changed in step with her taste in restaurants. "If I like a burger, I always ask how they make it," she said. She learned about meat by asking what they ground at the Union Square Cafe in New York, and at Zuni in San Francisco. From Taylor's Refreshers in St. Helena, she learned the importance of the right bun.

It has to be a classic, soft hamburger bun, she said, not sourdough, rustic roll or, perish the thought, pita bread. The important thing is the proportion of burger to bun. "It should be 50-50," she said, just right for absorbing juice and toppings.

Accept no substitutes

Silverton is a speedy, teach-as-she-cooks type. "The beauty of the burger for parties at home is choice," she said as she began splitting pickles. "Everybody gets to personalize their burger. Everyone gets to participate."

The toppings should be traditional, not wacky or fancy. "I'm not a foie gras-on-burger person," she said. But given the chance, she will go the extra mile to get deli pickles from Gus's in New York.

To her mind, every traditional topping must be represented, and the shopper should accept no substitutes. "Ketchup should be Heinz. Mayonnaise should be Best Foods in the West, Hellmann's in the East." The mayonnaise she likes to serve three ways: plain, souped up with chiles and another with garlic and tapenade. The recipes are part of her upcoming Knopf book in praise of cooking from cans, "Twist of the Wrist."

There should also be Tuscan Pepperoncini (she likes Mezzetta brand) and two types of mustard, both Dijon, one whole grain, one smooth. The lettuce must be iceberg, one crisp cupped leaf per burger. Sliced red onion -- one full slice per person. (Silverton salts and peppers the onions.)

Tomatoes: Right now, there should be thick slices of bun-size heirloom tomatoes. Brandywines, Russians, Beefsteak. There should be avocados, bought a week early to control the ripening. These should be sliced thickly, or they will turn to mush: in quarters or, at the smallest, in sixths. A light dressing of lemon will help prevent them from browning in the dish, but too much lemon will make them taste citric, so she recommends tossing in some chives to disguise inevitable blemishing.

There should be bacon (applewood-smoked), cooked short of crispness so it doesn't shatter in the mouth. Because people will pilfer from the toppings, you should cook two strips per guest.

No point in spoiling good meat with bad cheese. There should be a choice of three cheeses, she said: blue, cheddar and Gruyere. She had Point Reyes blue, Grafton cheddar and cave-aged Gruyere. Nicolas Beckman, who oversees the cheese counter at La Brea Bakery shop, also recommends Fiscalini or Straus cheddar.

"The blue and cheddar should be crumbled," said Silverton, holding out dishes brimming with broken cheese, "so they can be sprinkled on. That way you get to watch it melt. The Gruyere, this has to be served in slices."

And so to the meat. The morning of her burger party, Silverton sent me to her butcher, Huntington Meats at the Los Angeles Farmers Market. As I read from the order that she prepared, I asked for whole prime chuck, which already has 10% to 15% fat, to be ground with 13% sirloin fat added by weight.

The butcher smiled. "Nancy Silverton sent you, didn't she?" he asked.

It turned out that Huntington's lean mix has 5% fat, its standard mix 10% to 15%, but what they fondly called "Nancy's blend" has more like 20% to 28%.

"That's what gives the flavor," said the butcher. "Coarse ground, right?"

The difference, not just in flavor but also in texture, and pure out-of-this-world pleasure, would only become clear when I got the meat back to Silverton.

The patty, just so

Back at Silverton's house, the guests had arrived and she stood half swathed in an apron, ready to make patties. "For four people, you can just divide it," she said taking the bag. "For more, you want to measure the meat." We were 12, so she began taking small amounts of meat and setting them on a scale. "The perfect size is eight ounces," she said. Forming the burgers in a quick, light, slapping motion, she made them thick, nearly 2 inches high, so they wouldn't overcook, with rounded edges.

"With lean meat, the burgers don't hold together," she said. "Fat makes them easier to form. Feel this," she said, suddenly pressing a wad of raw ground beef in my palm. "It comes right together but you don't have a palm full of greasiness."

Aha. That is why the butcher expected she would want the fat and meat coarse ground. A fine ground would produce a smeary mess.

Second only to her fearlessness with fat proved her use of salt. As she formed burgers, she seasoned them, first going over them with a generous shower of kosher salt, about one-fourth teaspoon per burger, then passing again with six to eight turns each with a pepper grinder. Same treatment each side.

She uses the kosher salt because of the texture, Silverton said. "It handles well in the fingertips." She doesn't need a shaker and has more control. "It's important to do this only just before cooking them," she added, still salting. "Otherwise the salt will draw the moisture out of the meat."

Once she was ready to cook, only the cheeses and buns left the condiment table as she took up position over the barbecue. Every chef has an inner drill sergeant, and the better the chef, the less inhibited he or she is. In fact, Silverton might have two of them. She asked us to call our desired doneness-levels and cheese choices as she began cooking. As a tribe, we were medium-rare, Gruyere, but a sophisticate among us requested "trois fromages."

Even working over a hot open grill, as a sharp sizzle rose, Silverton seemed to come alive. "That's the sound you want," she said. A hot grill or a hot pan is crucial. Otherwise, low heat will require longer time in the pan, resulting in an overcooked burger.

For the barbecue chef working the fire, she added, the most important accouterments weren't a hat or apron, but a long-handled spatula and tongs, and long gloves.

Like a true cook, she knew the signs of doneness without tearing open the burger. "It's time to flip them when they don't stick," she said. Then, as soon as she flipped a half-done burger, she gave it a final touch of salt, this time sea salt, and cheese. In our case, Gruyere. "I love watching it dribble down the sides," she said.

A word about what she does not do. Unlike just about every other burger chef in the country, Silverton never, ever presses down on a burger with the spatula to force out the juices. Rather, as the burgers cooked, she toasted the oiled buns, handing them off to guests so they could begin personalizing. Toppings were more bottom-ings here. The burger came last.

Everyone seemed to want a little of everything: lettuce, avocado, bacon, tomato, onion, peppers, pickle. Option paralysis only seemed to set in over the mayonnaises. Here the Gruyere tribe split evenly among garlic, tapenade and chili.

Watching Silverton's youngest son, Oliver, made it clear why burger buns must be soft. As he took his towering burger to the table, before sitting down, he leaned over and squashed the burger with just enough weight to compress it into a bite-able state. It was as liberating as seeing the Queen Mother eat a quail with her hands. The world was now allowed to follow suit.

Biting into my first Silverton burger was a revelation. There wasn't a hint of fattiness about it, just moistness and a swelling chorus of flavors. Out of curiosity, I tried the burger of a little girl who wanted her burger well done. It was moist too.

After joy, shame. I had always thought inviting someone for "just a burger" was reassuring. Guests could buy beer instead of wine, bring kids, even dogs. I realize now that I meant I was going to give them an indifferent meal because I was feeling sentimental and lazy. Had I known the difference a little bit of care makes, my friends still could have brought beer, their kids and dogs, but we would have had what Silverton has convinced me may be the true American delicacy.